Is this block scrap?
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
Is this block scrap?
I finally got around to pulling the crank and getting the block ready to go to the shop, but after inspecting the bottom of the bores, cylinder 7 is looking mighty skimpy, and thats through my untrained eye. Its roughly 0.08" thick at the base. What do you guys make of this cylinder? (Please ignore my flat tire)
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Has it ever been bored before. Measure the bore of it right now. If it is only 4.000 or even 4.030 you are OK. If it is 4.040 or bigger I would pass on the block and find a better one. Don't worry what the bottom looks like.
Melting Slicks
Joined: Mar 2008
Posts: 2,336
Likes: 1
From: North Bellmore Ny
St. Jude Donor '09
The piston never reaches there anyway so as stated check where it is important.
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
Why is the block notched at the bottom of the bore?
So you guys would say as long as the bore is fine, regardless of how thick the cylinder wall is at the bottom, it would be fine?
Melting Slicks
Joined: Mar 2008
Posts: 2,336
Likes: 1
From: North Bellmore Ny
St. Jude Donor '09
The piston never has and friction with that part of the block. I have seen that part of the blocked notched out for rod bolt clearance on a friends race engine. it doesn't look the same as yours But If it works for high horsepower, That should be OK.
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
Ya, I mean you can clearly see where the bottom ring stops. I'm more concerned if I wanted to bore this out to 4.030 if I may be losing alot of cylinder wall.
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Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
Keep in mind that a .030 overbore will only take .015 off of each side of the cylinder. That's 1.5 tenths of a tenth of an inch. I don't think I've ever dealt with a 350 that wouldn't take at least a .030 overbore, most will take .040 and a few are fine at .060 over.
Melting Slicks
Joined: Dec 2003
Posts: 2,487
Likes: 1
From: Sydney
Is this the original motor? If so why worry about going so big with the overbore you really don't get that much extra capacity by over-boring the cylinders, just see what the machine shop recommends as the minimum to get good cylinders.
If you want more capacity a stroker crank is going to yield a much bigger capacity increase.
If you want more capacity a stroker crank is going to yield a much bigger capacity increase.
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
Is this the original motor? If so why worry about going so big with the overbore you really don't get that much extra capacity by over-boring the cylinders, just see what the machine shop recommends as the minimum to get good cylinders.
If you want more capacity a stroker crank is going to yield a much bigger capacity increase.
If you want more capacity a stroker crank is going to yield a much bigger capacity increase.
Thanks for the help guys, on with the build!
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
It actually costs less to go .010 over - that's just a hone, most shops can't bore .010 because of tool drift. Those are hard pistons to find, too. .020 is more common, most manufacturers start at .030
Thread Starter
Melting Slicks
Joined: May 2006
Posts: 3,438
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From: Raleigh NC
St. Jude Donor '13-'14
Le Mans Master
Joined: Jan 2006
Posts: 6,506
Likes: 139
From: Butler Pa
In order to install sleeves thick enough to overbore .125, you would need to cut the old cylinder completely away. You would essentially have wet sleeves and it would leave no support for the deck. In other words, it won't work.
Drifting
Joined: Dec 2005
Posts: 1,360
Likes: 3
From: NORTHEAST
We build a lot of circle track and street and strip performance engines and deal with probably 200 blocks a year and we have seen the bottom of cylinders like that before and its never been a problem so far.
And putting in sleeves for a .125 over bore not going to happen as the wrist pin side of the cylinder are between .070 to .160 thick which you would be boring into the water jackets, and there would be alot of cracking around the bolt holes when the heads are torqued down as we have seen this problem with the 400 blocks when sleeving them, The other problem is at the bottom of the cylinders as the webbing would get very thin and in a performance application there would be cracking from the step down through the main webbing.
If your building a performance engine here have it sonic tested for cylinder wall thickness and squared and decked so the cylinders are a true 45 degrees and 90 degrees to the crank and have it plate honed for good ring seal.
Good luck with your build Carl
And putting in sleeves for a .125 over bore not going to happen as the wrist pin side of the cylinder are between .070 to .160 thick which you would be boring into the water jackets, and there would be alot of cracking around the bolt holes when the heads are torqued down as we have seen this problem with the 400 blocks when sleeving them, The other problem is at the bottom of the cylinders as the webbing would get very thin and in a performance application there would be cracking from the step down through the main webbing.
If your building a performance engine here have it sonic tested for cylinder wall thickness and squared and decked so the cylinders are a true 45 degrees and 90 degrees to the crank and have it plate honed for good ring seal.
Good luck with your build Carl
